Abrogation of the Brd4-positive transcription elongation factor B complex by papillomavirus E2 protein contributes to viral oncogene repression.

Abstract

The cellular bromodomain protein Brd4 is a major interacting partner of the papillomavirus (PV) E2 protein. Interaction of E2 with Brd4 contributes to viral episome maintenance. The E2-Brd4 interaction also plays an important role in repressing viral oncogene expression from the integrated viral genome in human PV (HPV)-positive cancer cells. However, the underlying mechanism is not clearly understood. In host cells, Brd4 recruits positive transcription elongation factor b (P-TEFb) to stimulate RNA polymerase II phosphorylation during cellular and viral gene expression. P-TEFb associates with the C terminus of Brd4, which largely overlaps with the E2 binding site on Brd4. In this study, we demonstrate that E2 binding to Brd4 inhibits the interaction of endogenous Brd4 and P-TEFb. P-TEFb is essential for viral oncogene E6/E7 transcription in both HeLa and CaSki cells that contain integrated HPV genomes. E2 binding to Brd4 abrogates the recruitment of P-TEFb to the integrated viral chromatin template, leading to inactivation of P-TEFb and repression of the viral oncogene E6/E7. Furthermore, dissociation of the Brd4-P-TEFb complex from the integrated viral chromatin template using a Brd4 bromodomain dominant-negative inhibitor also hampers HPV E6/E7 oncogene expression. Our data support that Brd4 recruitment of P-TEFb to the viral chromatin template is essential for viral oncogene expression. Abrogation of the interaction between P-TEFb and Brd4 thus provides a mechanism for E2-mediated repression of the viral oncogenes from the integrated viral genomes in cancer cells.

• Authors: Junpeng Yan, Qing Li, Sam Lievens, Jan Tavernier, Jianxin You
• Journal: Journal of virology (J Virol) Vol. 84 Issue 1 Pg. 76-87 (Jan 2010) ISSN: 1098-5514 [Electronic] United States
• PMID: 19846528 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• BRD4 protein, human
• Cell Cycle Proteins
• DNA-Binding Proteins
• E2 protein, Human papillomavirus type 16
• E6 protein, Human papillomavirus type 16
• Nuclear Proteins
• Oncogene Proteins, Viral
• Papillomavirus E7 Proteins
• Repressor Proteins
• Transcription Factors
• oncogene protein E7, Human papillomavirus type 16
• Positive Transcriptional Elongation Factor B

Topics

• Alphapapillomavirus (genetics)
• Cell Cycle Proteins
• Cell Line
• Cell Line, Tumor
• DNA-Binding Proteins (physiology)
• Genes, Viral
• Humans
• Nuclear Proteins (metabolism)
• Oncogene Proteins, Viral (antagonists & inhibitors, genetics, physiology)
• Papillomaviridae (chemistry, physiology)
• Papillomavirus E7 Proteins
• Positive Transcriptional Elongation Factor B (antagonists & inhibitors, genetics, metabolism)
• Promoter Regions, Genetic
• Protein Binding
• Repressor Proteins (antagonists & inhibitors, genetics)
• Transcription Factors (metabolism)
• Transcription, Genetic